Soft tissue retractor

ABSTRACT

A tissue retractor device within the scope of the present invention generally includes a frame, an actuating mechanism, and a plurality of blades. The actuating mechanism generally includes at least one cam that encourages automatic toe-out of the blades. The tissue retractor eliminates the need for bulky secondary blade mechanisms to prevent undesired blade deformation at the surgical site. The toe-out motion occurs simultaneously along with the opening of the blades. The present invention further provides for depth adjustment of the blades by means of an adjustable screw assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national phase of PCT/US2015/018270 filedMar. 2, 2015, which claims priority to U.S. Provisional PatentApplication Ser. No. 61/946,986, filed Mar. 3, 2014, which isincorporated herein by reference.

FIELD OF THE INVENTION

The invention generally relates to the field of spinal orthopedics, andmore particularly to tissue retractor devices and blades used todistract soft tissue during surgical procedures.

BACKGROUND

The spine is a flexible column formed of a plurality of bones calledvertebrae. The vertebrae are hollow and piled one upon the other forminga strong hollow column for support of the cranium and trunk. Variousspinal disorders such as scoliosis, neuromuscular disease, and cerebralpalsy may cause the spine to become misaligned, curved, and/or twistedor result in fractured and/or compressed vertebrae. It is oftennecessary to surgically correct these spinal disorders to straighten oradjust the spine into a proper curvature.

Generally the correct curvature is obtained through surgical proceduresby manipulating the vertebrae into their proper position and securingthat position with a rigid system of screws, rods, intervertebralspaces, and/or plates. During the surgical procedure, a tissue retractormay be inserted into a surgical incision to pull tissue away from thesurgical site thus enlarging the viewing area for the surgeon. Tissueretractors form a surgical corridor including a proximal opening at theincision and a distal opening near the surgical site. Variousinstruments and implants may be inserted through the corridor. Exemplarytissue retractors may be found in U.S. Pat. No. 7,780,594 entitled“Retractor and Methods of Use” filed Oct. 6, 2006 and U.S. ApplicationPublication Number 2008/0114208 entitled “retractor” filed Sep. 24,2007.

The amount of tissue to be retracted depends upon the chosen approach aswell as various patient characteristics. For example, in a lateralapproach, more soft tissue may be present between the surgical incisionand the surgical site near the vertebrae than in a posterior approach.Patient anatomical differences may also require various lengthretractors. The size, shape, and configuration of the retractor may bechosen based on these as well as other factors.

Typical tissue retractors include two or more elongated blades withproximal ends attached to a housing that is in turn attached to asurgical table. Each blade assembly may be attached to a separateportion of the housing and include various adjustment features formanipulating the blades to adjust and enlarge the viewing area. Often,the tissue retractor may hold the blades close together in a tubularconfiguration for concentric insertion over dilation tubes along acommon longitudinal axis. The portions of the housing may translate orrotate relative to one another to gradually pull the blades apart fromone another to expand the surgical wound.

When a retractor is opened to distract soft tissue the resistance loadpressing on the distal end of the blades increases and causes conicaldeformation. As used herein “conical deformation” is when the distal endof the blades curve back towards the center of the portal openingforming a cone-like shaped tunnel where the distal opening at theexposed surgical site is smaller than the proximal portal opening. Theconical deformation of the blades also causes a reaction force thatpushes the retractor away from the surgical site. This requires that thesurgeon take extra precaution to prevent the blades from lifting off thebone surface as the retractor is opened.

In order to compensate for blade conical deformation most retractors usea secondary adjustment mechanism. This mechanism typically provides anindependent pivot action to cause the distal end of the blade to projectfurther out radially with respect to the proximal end of the blade-amotion referenced herein as “toeing out” or “toe out.” The blade may toeout by turning a screw that acts on a lever or by using a biasedtorsional spring. To properly align the opened retractor the surgeon isrequired to make two independent adjustments for each blade requiringadditional surgical time, and adds complexity and bulk to the jaws ofthe retractor. Due to the limited area available in the jaw area theadjustment mechanisms must be compact which limits the leverageavailable to counteract the torque generated by long length blades. Thislack of adequate counter leverage leads to very large loads that areapplied to small mechanisms. Failure and wear of the secondary blademechanism is a common complaint for such retractors. Accordingly, thereexists a need in the art to provide a soft tissue retractor thatadequately compensates for the conical deformation of the blades duringa procedure.

Furthermore, successful surgery is performed when using these retractorsby preventing soft tissue from encroaching into the surgical site byslipping under the distal end of the blade. The prime factor in managingthe dissection of soft tissue is maintaining contact of the distal endof the blades with the surface of the bone to prevent tissueencroachment. However, maintaining blade contact is difficult becausethe bone structure has a complex surface geometry that may cause theblade to lift as the blades are spread apart.

To reduce the risk of complications, current retractor systems rely ondocking and stabilization of the retractor rigidly with at least onesurgical table arm. It is often necessary for the surgeon to remove andreplace a blade with a blade of a different length to accommodate thevarying bone structure. This replacement is often required at the L4/L5disc space where the retractor frame may have to be tilted to avoidcontact with the iliac crest. Replacing a blade during a procedure addstime.

Adjustment mechanisms of the prior art have attempted to address theblade contact issue by the use of shims that project beyond the end ofthe blade and contact the bone surface. The shims are fit into a groovein the blade and slide down the entire length of the blade. Thisstructure provides the disadvantage of requiring the use of a separatecomponent that has to be mounted to an insertion instrument.

Another system to provide blade adjustment is the use of a telescopingblade that uses a nested blade that can be extended to the requiredlength. However, this method of using nested blades increases the bladecross-sectional area causing a more bulky blade system that requireslarger initial dilation and increased tissue expansion for an apertureduring a procedure.

Accordingly, there exists a need in the art to provide a soft tissueretractor providing for depth adjustment to prevent encroachment of softtissue during a procedure.

SUMMARY OF THE INVENTION

Provided herein are retractors configured to compensate for bladeconical deformation, and a blade having an adjustment mechanismconfigured to adjust the depth of the blade so as to reduce the need fora shim.

In one embodiment, a tissue retractor includes a frame having at leastone cam. The at least one cam is operatively connected to at least onecam follower. The cam follower may be a flat surface of a lever. Thelever has a blade. The blade is disposed on a distal end of the lever,and is generally orthogonally to the lever and is in a fixedrelationship to the cam follower. In some instances, the tissueretractor has at least two levers and each lever has a blade disposed ona distal end. The cam follower follows the cam so as to drive a distalend of respective blades away from each other as a respective proximalend of the at least two levers are squeezed towards each other.Accordingly, squeezing the levers together simultaneously opens asurgical corridor and causes the blades to toe out.

The frame may include a flange extending away from the frame towards thelevers. The cam is mounted to the flange. The cam is mechanicallycoupled to a portion of a lever and is configured to guide the leveralong an arcuate path so as to move the distal end of the blades awayfrom each other. The arcuate path is generally orthogonal to a diameterof the surgical corridor. The curved geometry of the outer surface ofthe cam permits the rotation of the cam follower abutting the cam toresult in rotation of the blade. Accordingly, a pair of cam followersbias against a pair of cams and the distal ends of the blades toe-out tocompensate for blade conical deformation. The arcuate path is disposedgenerally along a radius generally orthogonal to the respective levers,and accordingly, the distal end of a blade travels radially further thanthe proximal end of the blade when the levers are squeezed together.

In other embodiments, the cam follower is directly connected to an armof a ring retractor. Knobs corresponding with each arm and blade areadapted to rotate the arms and urge the cam followers along the cam toproduce toe-out.

One example embodiment includes a frame with a plurality of flanges. Yetin another embodiment, the frame is a ring structure having a pluralityof bores. Accordingly, the cam and cam follower automatically compensatefor the increasing load on the distal ends of the blades when the bladesare expanded in the tissue.

A blade having a blade adjustment mechanism allowing for adjustment ofthe depth of the blades of the tissue retractor is also provided. Insuch an embodiment, the retractor includes a lever having a housingadapted to connect with the adjustment mechanism. The adjustmentmechanism includes a threaded portion formed on the blade. Theadjustment mechanism further includes an adjustment screw, at least aportion of the adjustment screw is threaded, and the adjustment screwconnects the blade to the lever. The threaded portion of the blade ismechanically coupled to the threaded portion of the adjustment screwwherein rotation of the adjustment screw displaces the blade in avertical arrangement thereby allowing for adjustment of the depth of theblade. Furthermore, a spring loaded lock is connected to the threadedportion of the adjustment screw, the lock movable with the adjustmentscrew during depth adjustment.

Accordingly, the blades may be adjusted in depth so as to eliminate theuse of shims. Further, the depth adjustment mechanism is disposed on theblade itself and integrates with the blade locking mechanism therebyminimizing the size of the retractor so the surgeon has the maximumamount of visualization when taking photos or performing a procedure.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments set forth in the drawings are illustrative and exemplaryin nature and not intended to limit the subject matter defined by theclaims. The following detailed description of the illustrativeembodiments can be better understood when read in conjunction with thefollowing drawings where like structure is indicated with like referencenumerals and in which:

FIG. 1 is an exploded perspective view of one embodiment of the tissueretractor;

FIG. 2 is a front view of the tissue retractor shown in FIG. 1;

FIG. 3 is a perspective view of the first position of one embodiment ofthe tissue retractor shown in FIG. 1;

FIG. 4 is a perspective view of the second position of the tissueretractor shown in FIG. 1;

FIG. 5 is an isolated view of the offset cams of the tissue retractorshown in FIG. 1;

FIG. 6 is a close up perspective view of the tissue retractor shown inFIG. 1 illustrating the offset cams;

FIG. 7 is a perspective view of another embodiment of a tissue retractorhaving a ring frame;

FIG. 8 is an exploded of the tissue retractor shown in FIG. 8;

FIG. 9 is a top view of the ring frame shown in FIG. 7;

FIG. 10 is a bottom view the ring frame shown in FIG. 9;

FIG. 11 is a perspective view of the tissue retractor shown in FIG. 7 ina first position;

FIG. 12 is a perspective view of the tissue retractor shown in FIG. 7 ina second position;

FIG. 13 is a cross-sectional view of the tissue retractor shown in FIG.14 taken along line A-A, showing the actuating mechanism;

FIG. 14 is a top view of an example actuating mechanism;

FIG. 15 is a side view illustrating the initial angle of the arm piecerelative to the ring frame plane shown in FIG. 14;

FIG. 16 is a perspective view illustrating one of the plurality ofblades in an open and toed-out position;

FIG. 17 is a close up perspective view of a hinge;

FIG. 18 is a perspective view of an assembled toe angle adjuster with anadjustment knob;

FIG. 19 is a perspective view of the assembled toe angle adjuster shownin FIG. 18 without the adjustment knob respectively;

FIG. 20 is an exploded view of the example toe angle adjuster shown inFIG. 18;

FIG. 21 is a bottom view of the adjustment knob and arm piece shown inFIG. 20;

FIG. 22 is a perspective view of one embodiment of a tissue retractorand a blade with a depth adjustment mechanism;

FIG. 23 is a perspective view of the tissue retractor shown in FIG. 22with the blades removed;

FIG. 24 is a perspective view of a blade;

FIG. 25 is a side view of the retractor shown in FIG. 22 before depthadjustment;

FIG. 26 is a side view of the retractor shown in FIG. 22 after depthadjustment;

FIG. 27 is an exploded perspective view of the tissue retractor shown inFIG. 22;

FIG. 28 is a partially exploded perspective view of the retractor andthe blade shown in FIG. 22; and

FIG. 29 is a front view of the retractor shown in FIG. 28.

DETAILED DESCRIPTION OF THE INVENTION

A retractor configured to compensate for blade deformation is provided.A blade having an adjustment mechanism is also provided. The blade isconfigured to mount to a housing of a lever so as to adjust the depth ofthe blade.

In a first embodiment, the tissue retractor includes a frame having atleast one cam. The cam is operatively connected to a cam follower. Thecam follower and a lever are in a fixed relationship with respect toeach other. A blade is fixedly mounted to the distal end of the leverand is generally orthogonally to the lever. Accordingly, the blade isalso in a fixed relationship with the cam follower.

In some instances, the tissue retractor has two levers and squeezing thelevers results in simultaneous opening and “toeing-out” of the blades.Namely, each lever urges a cam follower along a cam so as to drive adistal end of the blades away from each other as the surgical corridoris formed. Each cam is mechanically coupled to a given blade andincludes a curved surface configured to guide a given cam follower andthe blade wherein the blade may compensate for the load exerted by thetissue. In another embodiment, two offset cams are provided tofacilitate the toe-out motion. The tissue retractor eliminates the needfor bulky secondary blade mechanisms to counteract undesired bladedeformation at the surgical site.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art. It must also be noted that as used herein and in the appendedclaims, the singular forms “a,” “an,” and “the” include plural referenceunless the context clearly dictates otherwise. Thus, for example,reference to a “lever” is a reference to one or more levers andequivalents thereof known to those skilled in the art, and so forth.

The words proximal and distal are applied herein to denote specific endsof components of the instrument described herein. A proximal end refersto the end of an instrument nearer to an operator of the instrument whenthe instrument is being used. A distal end refers to the end of acomponent further from the operator and extending towards a surgicalarea of a patient and/or the implant.

Now referring to FIG. 1, a tissue retractor having at least two leversis provided. The lever actuated tissue retractor 100 includes a firstlever 110, a second lever 120, a frame 134, and a plurality of blades140. As shown in FIG. 1 the tissue retractor 100 includes a cam 151having a cam surface 153. FIG. 1 shows the tissue retractor having twopair of cams 151, i.e. an upper cam 151 a and a lower cam 151 b,operatively coupled to each lever 110, 120. The pair of cams 151 a, 151b are offset each other on a respective side of the frame 134. Each cam151 a, 151 b includes respective cam surfaces 153 a, 153 b for which arespective cam follower 155 a, 155 b follows. However, it should beappreciated that the illustrations provided herein are not limiting tothe scope of the appended claims and that the tissue retractor may beconfigured to have only one cam 151 on each side of the frame 134coupled to a respective lever 110, 120. In such an embodiment where onlyone cam 151 is used, it should be appreciated that the geometry of thecam surface 153 along with the positioning of the cam 151 with respectto the blade 140 and the length of the blade 140 will determine the arclength and the range of motion of the toe-out of the distal end of theblade 140.

The cam surface 153 is mechanically coupled a respective cam follower155. The cam surface 153 is generally curved and configured to generatea toe-out movement of the blade 140. The blades 140 may be opened andclosed relative to each other by squeezing the first lever 110 andsecond lever 120 towards each other. It should be appreciated that,operation of one cam and cam follower need only be described, as theoperation of the other cam and cam follower is the same.

The cam 151 is mechanically coupled to a cam follower 155. The camfollower 155 is generally disposed at the proximal end of the blade 140.The cam 151 includes a curved cam surface 153 for which the cam followerrides 155 along and is guided along the path of the cam surface 153.Accordingly, the blade toes outs so as to compensate for the loadexerted by the tissue. In one embodiment, two offset cams 151 areprovided to facilitate the toe-out motion.

The cam follower 155 is urged along respective cams 151 a, 151 b and camsurfaces 153 a, 153 b. In other embodiments, a plurality of cams 151 areprovided. In this embodiment, the cam follower 155 directly connects tothe cam 151 without the use of pivot posts and spherical elements (suchas discussed below). The cam follower is adapted to connect and movedirectly on the cam surface 153.

The cam follower 155 is operatively connected to the cam surface 153.FIGS. 1-6 provide an illustrative example of a means for connecting thecam follower 155 to the cam 151. A first pivot post 112 and a secondpivot post 114 extend from opposing surfaces of a lever 110, 120. Aplurality of spherical elements 116 are disposed at the distal end ofthe pivot posts. In this particular embodiment, the spherical elements116 are spherical bushings that surround the distal end of the firstpivot post 112 and the second pivot post 114. The pivot posts 112, 114and the spherical elements 116 help facilitate the connection betweenthe cam 151 and the cam follower 155.

The first pivot post 112 and the second pivot post 114 are offset inrelation to one another in the same offset relation as the respectivecams 151. The first pivot post 112 and the second pivot post 114 alsoare offset in relation to one another in a distal and proximal directionalong a portion a length of the first lever 110 by an offset length L,such as shown in FIG. 5. The first post 112 is disposed distal to thesecond post 114 by offset length L. As shown in FIG. 1 the first andsecond pivot posts are disposed near the distal end of the first lever110. Also shown in FIG. 1 is the second lever 120. The second lever 120may be a mirror image of the first lever 110 with corresponding pivotposts, spherical elements 116, cam 151, cam surface 153 and camfollowers. In other embodiments not shown, the second lever 120 may notbe a mirror image of the first lever 110 such as having a differentoffset length between the pivot posts. In yet other embodiments, thesecond lever 120 may be an elongated extension of frame 134 or otherwiseattached to frame 134 such that the lever is immobile.

The frame 134 includes a plurality of flanges 132 extending outwardlyfrom opposite sides of the frame 134. The plurality of flanges 132 arepositioned such that the first lever 110 and the second lever 120 can bepositioned in a space between the flanges 132. Furthermore, the flanges132 have pivot sockets 136 corresponding to the first pivot post 112 andsecond pivot post 114 for both the first lever 110 and second lever 120.The cam surface 153 is disposed on the distal end of the respectiveflanges.

In one embodiment the pivot sockets 136 house the spherical elements 116to create a plurality pivot points 150 that are ball-and-socket jointsas shown in FIG. 2. The pivot points 150 in this particular embodimentare ball-and-socket joints and thus providing independent andmulti-axial movement at each pivot point 150 allowing the cam follower155 to follow the arcuate path of the cam surface 153. In embodimentsnot shown, the pivot posts may be cast or welded with spherical elements116.

In another embodiment not shown, the plurality of flanges 132 may extendalong the length of the frame 134. Although the flanges 132 of theexemplary embodiment of FIG. 1 extend away from the frame 134 at rightangles, one of ordinary skill in the art necessarily understands thatvarious flange geometries can be implemented provided that the flangeprovides proper structural support for the offset pivot points 150 andthe desired lever motion.

A plurality of blades 140 shown in FIG. 1 are attached to the distalends of the first and second levers 110, 120. In other embodiments, onlyone (or more than two) blade(s) 140 are used. The blades 140 may beattached by welding or may be cast as a continuous extension from agiven lever.

The plurality of blades 140 may be positioned at any angle relative tothe first and second levers 110, 120. In this particular embodimentshown in FIG. 1, the plurality of blades 140 are perpendicular to thefirst and second levers 110, 120. In other embodiments, the plurality ofblades 140 may have a more acute or more obtuse angle.

The plurality of blades 140 in a first position form a surgicalcorridor, which may be used with other medical instruments such as, forexample, a dilator. In the first position, the blades 140 may beinserted over the dilator. As the proximal ends of the first lever 110and second lever 120 are squeezed together, the distal ends of thelevers will simultaneously spread apart and rotate in a multi-planemotion causing the top and bottom sides of the levers 110, 120 to followseparate arc lengths and provide simultaneous opening and toeing actionto the plurality of blades 140. Movement of the plurality of blades 140away from each other will result in opening the surgical corridor and ina toe angle 144 in a second position, as shown in FIG. 2. The offsetlength L between the cams determines an opening angle 142 and toe angle144. The amount of toe angle 144 generated is a sinusoidal relation tothe opening angle 142 which increases in gain as the opening angleincreases.

The length L of pivot offset as shown in FIG. 5 can be adjusted toadjust blade deflection so that a parallel or a toed out condition willexist when the blades are fully opened. The bottom arc length Lb and thetop arc length Lt (shown in FIG. 5) may also be adjusted to adjust bladedeflection. Deflection is the amount that the blades are displacedaxially with respect to each other. Specifically, the amount the bladesare displaced during a procedure when soft tissue exerts a force againstthe blades.

The illustrative embodiments described depict uniform sized sphericalelements 116 and pivot pocket opening sizes. It is necessarily apparentto one of skill in the art that various combinations of sphericalelement 116 size, pivot pocket opening sizes, cam surface geometry andcam follower geometry may be implemented to achieve the desired openingangle and tilt angle required for various circumstances.

In an embodiment not shown, the lever actuated tissue retractor device100 may also include a biasing mechanism to return the plurality ofblades 140 to the first position (FIG. 4) or may be biased to return theplurality of blades 140 to the second position (FIG. 3). For example, aspring may be positioned between the first lever 110 and second lever120 such that upon relieving the compression force the levers willactuate the tissue retractor device to the first position.

Also not shown, is an embodiment that includes a lock mechanismdisplaced between the levers that can retain one or more open positions.In one embodiment, the lock mechanism can be a ratchet assembly. Inanother embodiment the lock mechanism can be opposing elongated memberswith corresponding serrations that interact to retain an open position.In yet another embodiment, the lock mechanism is combined with thebiasing mechanism such that the tissue retractor device willautomatically close with the release of the lock mechanism or vice versaautomatically open with the release of the lock mechanism.Alternatively, the lock mechanism can be similar to the lock mechanismillustrated in FIGS. 22-29.

Furthermore, the illustrative embodiment described changes to thegeometry of the cams 151 along one axis. However, one of ordinary skillin the art necessarily understands that the geometry of the cams 151 maybe changed along two axes to tailor the path of the tilting motionrelative to the blade opening as desired. Along with the geometry of thecam surface 153, the length of the plurality of blades 140 willdetermine the arc length exhibited by the distal ends of the blades 140as well as the amount of torque required to displace the tissue at thesurgical site. Thus, blades of various sizes both uniform andnon-uniform are contemplated within the scope of the present invention.

It should also be appreciated that the tissue retractor 100 may includemultiple blades 140. For example, the cam 151 and cam follower 155 maybe used in a three blade 140 configuration by having a central blade (orposterior blade) mounted to the frame 134. This embodiment would besimilar to the blade configuration as shown in FIG. 22.

Now referring to FIG. 7 another embodiment of a tissue retractor 200having a ring frame 230 is provided wherein the like elements arereferenced by like numbers increased by 100. The tissue retractor 200includes the ring frame 230, a plurality of drive assemblies 210, atleast one arm 220 and a plurality of blades 240. Each blade 240 isconnected in a generally orthogonal arrangement to a respective arm 220.The tissue retractor 200 includes at least one cam 251 and respectivecam surface 253 (FIG. 8). A cam follower 255 is coupled to the camsurfaces 253 of the cam 251.

The cam 251 includes the cam surface 253 which is curved along a radiusgenerally orthogonal to the plane of the ring frame 230 and thus isconfigured to guide a respective blade 240 to toe out wherein the blade240 may compensate for the load exerted by the tissue.

The cam 251 and cam follower 255 are coupled together by a first andsecond pivot post. The first and second pivot post 212, 214 allow thecam follower 255 to rotate, move and pivot about the cam surface 253.Accordingly, the cam follower 255 may follow the cam surface 253.

In this embodiment, the cam follower 255 connects to an arm 220. The arm220 includes a blade 240 fixedly mounted to a free end of the arm 220.The arm 220 is configured to swing inwardly within the ring frame 230.As the arm 220 swings inwardly, the cam follower 255 follows the camsurface 253 resulting in a toe-out motion of the blades 240.

The ring frame 230 may also include a boss 270 to enable the attachmentof the ring frame 230 to a stabilization surgical arm (not shown). Thestabilization surgical supports the retractor during surgery.

An illustration of a drive assembly 210 is shown in FIGS. 7 and 8. Thedrive assembly 210 includes a knob 211 coupled to barrel 213 by havinginternal threads corresponding to the threads on the proximal end ofbarrel 213. In other embodiments, the knob 211 is coupled as a snap onpiece to the proximal end of barrel 213 or the knob 211 may be glued,welded, or cast as part of barrel 213.

The barrel 213 is retained in bore 231 which essentially acts as abushing allowing barrel 213 to rotate around a longitudinal axis 201. Assuch, barrel 213 may include bearings or any other structure that isconducive to rotation. The diameter of bore 231 is such that therotation of barrel 213 remains substantially on a single longitudinalaxis 201. The distance between collar 213 a and detachable collar 211 issuch that the lateral movement of barrel 213 is prevented.

The barrel 213 has internal threads that correspond to the threads on aclevis engagement piece 216 such that rotation of barrel 213 actuated byknob 211 results in the translation of the rotational movement of barrel213 to lateral movement of the clevis engagement piece 216 and theclevis 215 in the proximal and distal direction along longitudinal axis201. In other embodiments not shown, lateral movement of the clevis maynot require a threaded barrel. For example, knob 211 may have a centralbore with corresponding threads to clevis engagement piece 216 obviatingthe need for a threaded barrel. In other embodiments of the driveassembly 210, the knob 211 may be omitted and instead the clevisengagement piece 216 may be elongated threaded piece or a rack such thatthe clevis 215 can be actuated by a ratcheted pinion or coupled toanother device. It is necessarily apparent to one of ordinary skill inthe art that the drive assembly 210 embodiment for imparting thedescribed motion is only for illustrative purposes, and all structuresthat impart similar motions are contemplated within the scope of thepresent invention.

The clevis 215 is coupled to the arm piece 220 via a pivot pin 219hinging a clevis knuckle 217 with an arm piece knuckle 221 to create anelbow-like joint or hinge. The pivot pin 219 in this particularembodiment passes through a track 236 to facilitate controlled movementof clevis 215 along longitudinal axis 201. The pivot pin 219 in otherembodiments not shown may be a quick pin or any similar type of pinwhich enables detachability of the arm piece 220. The clevis 215 in thisparticular embodiment incorporates a yoke-type conformation wherein thearm piece knuckle 221 is disposed within the clevis knuckle 217. Thepivot pin 219 is passed through the clevis 215 and knuckle 221, therebysecuring the clevis 215 to the knuckle. The knob 211 may be rotated soas to urge the clevis 215 forward, however the pin 219 translates theforward advancement of the clevis 215 into rotational movement, whereinthe knuckle 217 and the arm piece 220 swing outwardly as one piece,carrying the blade 240. In other embodiments not shown, the pivot pin219 may be a grommet wherein the clevis knuckle 217 does not have theyoke-like conformation as shown in FIG. 7. Other embodiments wherein theclevis knuckle 217 does not have a yoke-like conformation are fullycontemplated within the scope of the present invention provided that thedesired hinge can be achieved.

The arm piece 220 in this embodiment includes a first pivot post 212 andsecond pivot post 214 which are offset from each other. The first pivotpost 212 includes the cam 251 having a generally curved surface. Thesecond pivot post 214 includes the cam follower 255 having a generallycurved surface. The cam 251 is fixedly mounted to an end portion of thefirst pivot post 212 and the cam follower 255 is fixedly mounted to anend portion of the second pivot post.

Now referring to FIGS. 9 and 10 which illustrate the bottom view of ringframe 230 and FIG. 9 which illustrates the top view of ring frame 230,the arm piece 220. The first and second spot face 233, 235 have anaperture 233 a through which the first pivot post 212 passes through.The arm piece 220 has a yoke-like structure with two prongs 224 a, 224 bhaving respective apertures 224 c, 224 d (FIG. 8). The spot faces 233,235 fit within the prongs 224 a, 224 b of the arm piece 220. The firstand second pivot posts 212, 214 are inserted into respective apertures224 c, 224 d. The apertures 224 c, 224 d are offset from each other withrespect to a longitudinal axis of the arm piece 220. Aperture 224 d isaligned with aperture 233 a wherein the first pivot post 223 is mountedtherein. The end of the first pivot post 212 includes a cam 251 having acam surface 253 and the end of the second pivot post 214 includes a camfollower 255. The cam 251 and cam follower 255 are disposed within theinterior of the yoke-like arm piece 220. The cam 251 and cam follower255 may or may not each have a threaded bore configured to receivethreaded ends (not shown) of respective first and second pivot posts212, 214 so as to couple the arm piece 220 to ring frame 230 such thatthe cam 251 and cam follower 255 are mounted to their correspondingpivot sockets wherein the cam follower 255 is pressed against the camsurface 253. Accordingly, opening of the blade 240 urges the camfollower 255 along the arcuate path of the cam surface 253 causing thedistal end of the blade 240 to toe out as the blade 240 is opened. Itshould be appreciated that the blade 240 may be opened by rotating knob211 as described above.

The tissue retractor 200 may further include a blade locking mechanism228 by which the blade 240 is coupled to the arm piece 220. In theexample embodiment shown in FIGS. 8 and 20, the blade locking mechanism228 includes a slot 228 a, a latch 228 b, a latch slot 228 c, a lockingpin 228 d, and a set pin 228 e. The engageable end of latch 228 b isinserted into latch slot 228 c and coupled to the locking pin 228 d bydisposing a set pin 228 e through aligned openings on the latch 228 band locking pin 228 d. The latch 228 b or locking pin 228 d is biasedsuch that the locking pin 228 d protrudes into the stub receiving slot228 a until the latch 228 b is actuated to withdraw the locking pin 228d from the stub receiving slot 228 a. The distal end of the locking pin228 d is angled as shown in or rounded such that a blade tang 242 canslide into the stub receiving slot 228 a and be secured as the lockingpin 228 d sets into a notch on the blade tang 242. In other embodimentsnot shown, the blade is welded or is part of a continuous cast of thearm piece 220.

An isolated view of the arm piece knuckle 221 attachment point 221 a andclevis 215 is provided in FIG. 17. The ring frame 230 is purposefullyomitted to show that the knuckle 221 may be configured to provide adegree of freedom at the hinge region allowing the arm piece 220 toexhibit the desired range of motion. In one embodiment, the attachmentpoint 221 a is an orifice with a diameter greater than that of the pivotpin 219. In other embodiments, the attachment point 221 a may becomprised of flexible material. One of ordinary skill in the artnecessarily understands that the attachment point 221 a can be anystructure that provides the degree of freedom to allow the arm piece 220to exhibit movement resulting in the desired toeing out motion of theplurality of blades 240.

In an embodiment as shown in FIG. 15, a normal plane N of the offsetpivots generated by the cam 251 and cam follower 255 is angled relativeto the top plane of the ring frame 230, represented by the dashed line,by between 1°-10°. Thus when the blades 240 are closed the transverseaxis of the arm piece 220 is angled. As shown in FIG. 16, this anglecauses the distal tip of the blade 240 to sweep in a downward direction300 as the blade 240 opens. This downward sweep of the arm piece 220compensates for the shortening of the effective length of the blade 240due to the upward arc of the toeing blade 240 causing the tip of theopening blade 240 to remain in the same plane of the distal tips in theclosed first position. This action prevents the opening blade 240 fromlifting off the vertebral body as the blade 240 is toed out, whichallows the surgeon to actuate the toeing out motion of the blade 240without soft tissue slipping under the blade tip.

As shown in FIGS. 18 and 19, the tissue retractor 200 may furtherinclude a toe angle adjuster 260. The toe angle adjuster 260 adjusts theinitial tilt angle of the blade 240 in the first position. As shown inFIGS. 20 and 21, an embodiment of the toe angle adjuster 260 includes anadjustment knob 261, a bias spring 262, a set screw 263, a plate 265, ananchor stub 266, a set screw slot 267, an axle slot 268, and anadjustment track 269. In this exemplary embodiment, the plate 265 isdisposed within the arm piece 220 such that the top surface of the plate265 is in contact with the arm piece 220 and the second pivot post 214opposes the first pivot post 212 in a similar position as the embodimentshown in FIGS. 13 and 14. When properly fit, an adjustment post 265 aprotrudes through adjustment track 269 and extends beyond the plane ofthe arm piece 220 surface. An axle 265 b fits into axle slot 268 andprovides the rotational axis for plate 265. The adjustment knob 261 isfit such that the set screw slot 267 is aligned with a central bore 261a, the protruding adjustment post 265 a is housed within thedisplacement track 261 b, and the anchor stub 266 is housed in acorresponding anchor notch 261 c.

Adjustment knob 261 is configured to linearly displace the adjustmentpost 265 a within the length of adjustment track 269. As shown in FIG.21, the length of the adjustment track 269 corresponds to thedisplacement between the two ends of the displacement track 261 b. Inthe example embodiment shown in FIG. 20, the second pivot post 224 andthe cam follower 255 are disposed on the bottom surface of plate 265,thus displacement of the adjustment post 265 a along the adjustmenttrack 269 displaces the cam follower 255 with respect to the cam 251.The transferred motion causes rotational motion at the pivot points 251and subsequent rotation of the arm piece 220 and toeing out of the blade240 while in the first position. The depiction in FIG. 21 is merely forillustrative purposes and is not drawn to scale.

The anchor stub 266 fits into one of the plurality of anchor notches 261c to immobilize the adjustment knob 261 to a pre-calibrated positionthus maintaining the desired initial toe angle. As illustrated in FIGS.18 and 19 the adjustment knob 261 may have calibrated demarcationscorresponding to each of the anchor notches 261 c. The demarcations maybe calibrated to provide initial toe angle adjustment from about 0° toabout 45°, preferably from about 0° to about 15°, and most preferablyfrom about 0° to about 10°. The demarcations can be incremented at about0.5° increments to about 10° increments.

As shown in FIG. 20, the set screw 263 has a rim 263 a preventing thescrew from immobilizing the adjustment knob 261. Bias spring 262 isdisposed about the set screw 263 and between the top surface of theadjustment knob 261 and the set screw head. The bias spring 262 providessufficient normal force on the adjustment knob 261 such that the anchornotch 261 c housing anchor stub 266 can maintain the selected initialtoe angle. The bias spring 262 further allows the surgeon to pull up onthe adjustment knob 261 to remove anchor stub 266 from anchor notch 261c and rotate the adjustment knob 261 to another position.

Now referring to FIGS. 22-26, a blade 470 having a blade mounting andadjustment mechanism 500 allowing for connection of the blade 470 to alever 402 and adjustment of the depth of the blade 470 of the tissueretractor 400 is provided.

The blade 470 may be used with a retractor 400 having a housing 406adapted to connect with the adjustment mechanism 500 of the blade 470.It should be appreciated that any retractor, including the retractorsdisclosed herein may be adapted to include the housing 406. Theadjustment mechanism 500 includes a threaded portion 466 formed on theblade 470. The adjustment mechanism 500 further includes an adjustmentscrew 480, at least a portion of the adjustment screw being threaded.The adjustment screw 480 connects the blade 470 to the lever 402 bymeans of the housing 406. The threaded portion 466 of the blade 470 ismechanically coupled to the threaded portion of the adjustment screw 480wherein rotation of the adjustment screw 480 displaces the blade 470 ina vertical arrangement thereby allowing for adjustment of the depth ofthe blade 470.

In this embodiment, the adjustment mechanism 500 is mounted to the blade470 of the retractor. Furthermore, a spring loaded locking lever 408 isconnected to the threaded portion of the adjustment screw 480, thelocking lever 408 movable with the adjustment screw 480 during depthadjustment.

Accordingly, the blades 470 may be adjusted in depth so as to eliminatethe use of shims used to increase the overall length of a typical blade.Further, the depth adjustment mechanism is disposed on the blade 470itself and integrates with the blade 470 itself thereby minimizing thesize of the retractor so the surgeon has the maximum amount ofvisualization when taking photos or performing a procedure.

An important factor in blade 470 height adjustment is the size of themount. As used herein, the mount refers to the structure for supportingthe blade 470 to the retractor. The adjustment mechanism 500 allows forboth adjustment and attachment of the blade 470 to the lever 402, whilemaintaining a smaller physical dimension relative to currently knownmounts. Minimizing the size of the mount provides the surgeon with agreater field of view and camera angle when taking photos or performinga procedure. Having a blade 470 with an adjustment mechanism describedherein minimizes the size of the blade mount by integrating bladelocking and height adjustment features in one package.

Once locked, the rotating adjustment screw 480 allows for continuousblade height adjustment. FIGS. 22-29 illustrate several embodiments of aretractor 400 having an adjustment mechanism 500. Although the disclosedembodiments illustrate a retractor 400 having two handles 410 squeezableto facilitate expansion of the blades 470, other embodiments such as thering embodiment may also include the adjustment mechanism 500 describedherein.

The retractor assembly 400 includes at least one lever 402 having adistal end 404. The distal end 404 is adapted to connect to the blade470. The levers 402 are generally elongated and are adapted to connectwith the blades 460 at a housing 406. The blades 470 connect and lock tothe distal end 404 of the lever 402 by means of the locking lever 408.The levers 402 further include handles 410 with locking mechanisms 412,414. The retractor 400 further includes mounting members 416, 418adapted to mount to at least one surgical table arm 490. In the presentembodiment, the retractor 400 is shown having a posterior arm 420providing for connection to a third posterior blade. The posterior bladearm 420 also includes the adjustment mechanism 500.

The blade 470 includes a distal end 471 and a corresponding proximal end473. A curved arm 474 extends outwardly from the proximal end of theblade 470 and is generally orthogonal to the axial length of the blade470. The curved arm 474 is adapted to hold the adjustment mechanism 500and to place the blades 470 in a position to form a generallycylindrical surgical corridor when pressed together in a first positionas shown in FIG. 22. The adjustment mechanism 500 is partially shown inFIG. 24 and fully illustrated in FIGS. 28 and 29. The adjustmentmechanism 500 includes a partially open bore 464 at the distal end ofthe arm 474. The bore 464 includes a threaded portion 466 along at leasta portion of the interior surface of the bore 464. The adjustmentportion 500 further includes an outer surface 462 adapted to form agenerally smooth outer surface with the lever 402. Indentations 472 areprovided to connect with the distal end of the lever 402.

The adjustment mechanism 500 includes the adjustment screw 480. Theadjustment screw 480 includes a threaded portion 482 and a head 484. Thethreaded portion 482 covers at least a portion of the outer surface 481of the adjustment screw 480. The threaded portion 482 is adapted toconnect with the threaded portion 466 of the bore 464. An upper lip 468may be further provided at an upper portion of the bore 464. The lip 468may be slightly crimped to prevent the adjustment screw from dislodging.Alternatively or in addition to, a harness 486 is provided to preventdislodgment of the adjustment screw 480 during adjustment. The harness486 includes an aperture to accept the set screw 488. The set screw 488is adapted to secure to the aperture 489 of the arm 474 of the blade470. The harness 486 includes a U-shaped portion 491 adapted to connectto the adjustment screw 480.

The distal portion of the lever 402 is adapted to hold the locking lever408. The locking lever 408 includes a notch 492 adapted to connect tothe threaded portion 482 of the adjustment screw 480. The locking lever408 further includes an aperture 493 adapted to connect to a pin 434.The pin 434 allows for the locking lever 408 to pivot and thus releasefrom the adjustment screw 480. The locking lever 408 includes a handleportion 495 allowing the user to rotate the locking lever 408 about thepivot pin 434. Rotation of the locking lever 408 results in unlocking ofthe adjustment mechanism 500 and thus release of the blade 470.

The adjustment mechanism 500 is mounted to the blade 470 and directlylocks to the locking lever 408. Once the locking lever 408 is released,the entire blade 470 is also accordingly released and thus can beremoved. The locking lever 408 is mounted to the lever 402 by the pivotpin 434 that allows the top of the locking lever 408 to act against aspring and thus swing open. The threaded portion 482 of the adjustmentscrew 480 slides down a ramped portion 497 on the locking lever 408causing the lever 408 to swing open as the blade 470 is inserted intothe lever 402. The threaded portion 482 of the adjustment screw 480 hasdefined edges that create a cylindrical shape which engages the notch492 of the locking lever 408. The notch 492 includes a plurality ofgenerally planar surfaces arranged to securely accept the threadedportion 482 of the adjustment screw. The threaded portion 482 of theadjustment screw 480 is captured by the indentation 492 and held in aclosed position by a spring that acts behind the locking lever 408 andis contained within the lever 402. When the locking lever 408 is closedaround the threaded portion 482 of the adjustment screw 480, theadjustment screw 480 is free to rotate and thus adjust the height ordepth of the blade 470.

Depth adjustment of the blade is accomplished by rotation adjustmentscrew 480. Specifically, rotation head 484 actuates rotation of theadjustment screw 480. In the present embodiment, a wrench is used toturn the adjustment screw at the head 484. In other embodiments, a nutor other handle connected to the adjustment screw may be utilized torotate the adjustment screw 480.

The threaded portion 482 of the adjustment screw 480 mates with athreaded portion 466 of the bore 464. As the adjustment screw 480 isrotated, the blade 470 can be raised or lowered as the threaded portion482 of the adjustment screw 480 moves up and down in the bore 464. Thethreaded portion 482 of the adjustment screw 480 mates with the threadedportion 466 of the bore 464. Rotation of the adjustment screw 480results in a downward or upward motion of the blade 470. The arm 474 ofthe blade 470 accordingly is displaced as the adjustment screw isrotated.

FIGS. 25 and 26 illustrate rotation and height adjustment of the blade470. FIG. 25 illustrates the retractor 400 having the blade 470 beforeany adjustment. A bone surface 460 is provided at the distal end 471 ofthe blade 470. As illustrated in FIG. 25, before a height adjustment ofthe blade 470, the distal end 471 is spaced apart from a bone surface460. The gap ΔX between the bone surface 460 and the distal end 471 ofthe blade 470 may result in soft tissue encroaching into the surgicalsite 502. In the present embodiment, ΔX ranges between 5-6 millimeters.However, in other embodiments, ΔX may range up to 10 millimeters. FIG.26 illustrates the blade 470 after it has been adjusted allowing thedistal end 471 of the blade 470 to contact the bone 460. This adjustmentthereby prevents encroachment of soft tissue into the surgical site 502.

In the present embodiment, a third posterior blade arm 420 is alsoprovided. The arm 420 may also be adjusted in a forward and rearwarddirection by means of the adjustment screw 442. Rotation of theadjustment screw 442 results in forward and rearward motion of the arm420. In the present embodiment, the adjustment screw 442 is adjustedwith a hexagonal wrench. In other embodiments a handle or other rotationnut may be provided for adjustment. The blade connected to the posteriorblade arm 420 is typically the blade that is anchored to the vertebraeor the annulus of the disc/the other wall of the disc itself.

The retractor 400 may be further configured to automatically perform atoe-out motion when the handles 410 are squeezed together. Withreference now to FIG. 27, each lever 402 includes at least one camfollower 455 mounted thereto. In the present embodiment, the lever 402includes two cam followers 455 a, 455 b. The cam follower 455 a ismounted to the arm 402 within the aperture 403. The cam follower 455 ais mounted by means of a post 432 connected to the lever 402. The post433 includes a threaded portion 431 adapted to secure to a lower portionof the lever 402. The post 432 extends through the lower portion of thelever 402 and connects directly with the cam follower 455 a.

The cam follower 455 b connects to the lever 402 by means of a plate457. The plate 457 is mounted to the arm 402 by a post 433. The post 433includes a threaded portion 435 adapted to secure to an upper portion ofthe lever 402. The post 433 extends through the upper portion of thelever 402 and connects directly with the plate 457. The plate 457includes a post (not shown) extending orthogonally from a lower surface459. The post is adapted to connect with and secure the cam follower 455b to the plate 457.

Corresponding cams 451 a, 451 b include curved inner cam surfaces 453 a,453 b adapted to operatively connect with respective cam followers 455a, 455 b. The cams 451 a, 451 b are fixedly connected to the flange 430within the apertures 439 a, 439 b. In this embodiment, the cams 451 a,451 b and corresponding apertures 439 a, 439 b are offset. The camfollowers 455 a, 455 b rest within the respective cams 451 a, 451 b andare free to pivot and rotate within the cams 451 a, 451 b when thehandles 460 are squeezed together. When the handles 460 are squeezedtogether, the lever 402 is free to pivot about the cams 451 a, 451 bresulting in independent pivot action of the blade 470 (mounted to thelever 402) to cause the distal end of the blade to project out radiallywith respect to the proximal end of the blade.

In this embodiment, the cam followers 455 a, 455 b are generallyspherical elements having a rounded outer surface. Correspondingly, thecam surfaces 453 a, 453 b have a concave generally spherical surface. Itshould be appreciated that other geometries of both the cam followers455 a, 455 b and the cam surfaces 453 a, 453 b may include varyinggeometry to accommodate the toe-out requirements of the blade 470.

The blades 470 in a first position form a cylindrical surgical corridor,which may be used with other medical instruments such as, for example, adilator. In the first position, the blades 470 may be inserted over thedilator. As the levers 402 are actuated, the levers 402 willsimultaneously be urged together and rotate in a multi-plane motioncausing the top and bottom sides of the jaws to follow separate arclengths providing simultaneous opening and providing toeing action tothe plurality of blades 470. Expansion of the plurality of blades 470will result in a toe angle in a second position (partially open viewshown in FIGS. 25 and 26). The offset length between the cams 451determines the opening angle and toe angle. The amount of tilt generatedis a sinusoidal relation to the opening angle which increases in gain asthe opening angle increases.

The blades 470 are attached to the distal ends of the levers 402. Inother embodiments, only one blade 470. The blades 470 may be attached bywelding or may be cast as a continuous extension from the lever. Inother embodiments not shown, the blades 470 are detachable and havetangs disposed at the proximal end of each blade 470. The blade tangsfit into corresponding recess disposed at the distal end of each lever.

The curved portion 422 is adapted to be inserted through the lever 402.It is inserted through an aperture with a larger dimension thus allowingthe curved member 422 tolerance within the aperture during toe-out. Theradius of curvature of the curved arm 422 corresponds to the radius ofthe pivot of the lever 402. The release mechanism 412 connected to thehandle 410 communicates with the curved portion 422. As the releasemember 412 is actuated, the curved portion is disengaged. Actuation ofthe release mechanism 412 results in release of the locking member 413.

The locking member 413 connects with the curved portion 422 and thenotch portions 424 of the curved portion 422. In an alternativeembodiment, the locking portion 413 is adapted to have a pin or otherconnection portion connecting to a notch portion on the curved member.Such an adjustment lock will allow the surgeon to slightly advance backif the retractor was open too far. Without the locking portion 413, theforces on the blades 470 would force the retractor mechanism shut, orslam the retractor shut. The locking mechanism with slight adjustmentwould allow for the surgeon to gradually close the retractor for slightinward adjustment. The locking member 413 may include a twisting deviceso that when you squeeze the release lever the handle can be movedinward without the retractor slamming shut.

While the invention has been described in connection with variousembodiments, it will be understood that the invention is capable offurther modifications. This application is intended to cover anyvariations, uses or adaptations of the invention following, in general,the principles of the invention, and including such departures from thepresent disclosure as, within the known and customary practice withinthe art to which the invention pertains.

1. A tissue retractor comprising at least two blades, the at least twoblades forming a surgical corridor, the tissue retractor comprising: aframe having at least one cam; and a cam follower operatively connectedto a blade, the cam follower movable with respect to the frame, whereinthe cam follower is adapted to follow the cam so as to drive a distalend of one of the at least two blades further away than a proximal endof said one of the at least two blades during actuation of theretractor, wherein the cam includes a cam surface having an arcuate pathon a plane generally orthogonal to a diameter of the surgical corridor.2. The tissue retractor of claim 1 wherein the cam follower is connectedto a lever.
 3. The tissue retractor of claim 2, having a flangeextending away from the frame towards the lever, the flange having thecam.
 4. The tissue retractor of claim 2 wherein two levers are provided,each of the two levers biased against a respective cam, each of the twolevers having a cam follower, each cam follower engaged with arespective cam.
 5. The tissue retractor of claim 1, wherein two cams areprovided, each cam offset the other with respect to a longitudinal axisof the lever.
 6. The tissue retractor of claim 4 wherein each of the twolevers are mirror images of one another.
 7. The tissue retractor ofclaim 1 wherein the blade includes an adjustment mechanism connectedthereto, the adjustment mechanism configured to operatively adjust thedepth of the blades during a procedure
 8. The tissue retractor of claim1, further including a toe adjuster, the tow adjuster configured toadjust the tilt angle of the blade.
 9. The tissue retractor of claim 1,wherein the frame is a ring frame.
 10. The tissue retractor of claim 10wherein the ring frame includes a plurality of arms, the blades areconnected to each of the plurality of arms, each of the plurality ofarms are configured to pivot within the ring frame, wherein in a firstposition the plurality of blades form a surgical corridor which may beexpanded by pivoting the plurality of arms.
 11. A blade for use with atissue retractor, the blade comprising: an adjustment mechanism, theadjustment mechanism having a threaded adjustment screw adapted torotate within the blade, wherein as the adjustment screw is rotated, theblade is displaced vertically thereby allowing for adjustment of thedepth of the blade with respect to the tissue retractor.
 12. The bladeof claim 12 wherein the blade includes a curved arm generally orthogonalto an elongated axis of the blade, the curved arm adapted to hold theadjustment mechanism.
 13. The blade of claim 12 wherein the bladeincludes a threaded bore adapted to connect with the adjustment screw ofthe adjustment mechanism.
 14. The blade of claim 12 wherein theadjustment mechanism is adapted to connect with a housing on the tissueretractor.
 15. A tissue retractor having a blade adjustment mechanismallowing for adjustment of the depth of the blades of the tissueretractor, the retractor comprising: at least two levers, each of thelevers having a housing at the distal end of the lever; at least oneblade having an adjustment mechanism mounted thereto, the adjustmentmechanism having an adjustment screw, at least a portion of theadjustment screw being threaded, the adjustment screw connecting theblade to the housing of the lever, a threaded portion of the bladeconnecting to the threaded portion of the adjustment screw, wherein asthe adjustment screw is rotated the blade is displaced in a verticalarrangement thereby allowing for adjustment of the depth of the blade.16. The tissue retractor of claim 16 wherein a spring loaded lock isconnected to the threaded portion of the adjustment screw, the lockmovable with the adjustment screw during depth adjustment.
 17. Thetissue retractor of claim 16 wherein the adjustment mechanism isconnected to an extended arm portion of the blade.
 18. The tissueretractor of claim 16 wherein ratcheting is incorporated to providesensory feedback to the user regarding the amount of movement of theblade.
 19. The tissue retractor of claim 16 wherein the blade has amaximum distal displacement of up to 10 millimeters.
 20. The tissueretractor of claim 16 wherein the blades automatically toe-out duringactuation of the levers as the levers pivot about at least one camsurface allowing for simultaneous opening of the blades and automatictoe-out of the distal ends of the blades.